The invention relates generally to stators for use with progressive cavity pumps or motors; more specifically, to a stator having at least one transducer therein and methods of forming and using the stator.
Progressive cavity pumps or motors, also referred to as a progressing cavity pumps or motors, typically include a power section consisting of a rotor with a profiled helical outer surface disposed within a stator with a profiled helical bore. The rotor and stator of a progressive cavity apparatus operate according to the Moineau principle, originally disclosed in U.S. Pat. No. 1,892,217, herein incorporated by reference.
In use as a pump, relative rotation is provided between the stator and rotor by any means known in the art, and a portion of the profiled helical outer surface of the rotor engages the profiled helical bore of the stator to form a sealed chamber or cavity. As the rotor turns eccentrically within the stator, the cavity progresses axially to move any fluid present in the cavity.
In use as a motor, a fluid source is provided to the cavities formed between the rotor and stator. The pressure of the fluid causes the cavity to progress and imparts relative rotation between the stator and rotor. In this manner fluidic energy can be converted into mechanical energy.
As progressive cavity pumps or motors rely on a seal between the stator and rotor surfaces, one of or both of these surfaces can include a resilient or dimensionally forgiving material. Typically, the resilient material has been a relatively thin layer of elastomer disposed in the interior surface of the stator. A stator with a thin elastomeric layer is typically referred to as thin wall or even wall design.
An elastomeric lined stator with a uniform or even thickness elastomeric layer has previously been disclosed in U.S. Pat. No. 3,084,631 on “Helical Gear Pump with Stator Compression”. The prior art has evolved around the principle of injecting an elastomer into a relatively narrow void between a stator body with a profiled helical bore and a core (e.g., mandrel) with a profiled helical outer surface. The core is then removed after curing of the elastomer and the remaining assembly forms an elastomeric lined stator. The elastomer layer is essentially the last component formed.
The stator bodies mentioned above have a pre-formed profiled helical bore. The profiled helical bore is generally manufactured by methods such as rolling, swaging, or spray forming, as described in U.S. Pat. No. 6,543,132 on “Methods of Making Mud Motors”, incorporated by reference herein. Similarly, a profiled helical bore can be formed by metal extrusion, as described in U.S. Pat. No. 6,568,076 on “Internally Profiled Stator Tube”, incorporated by reference herein. Further, various hot or cold metal forming techniques, such as pilgering, flow forming, or hydraulic forming, as described in P.C.T. Pub. No. WO 2004/036043 A1 on “Stators of a Moineau-Pump”, incorporated by reference herein, can be used to form a stator body with a profiled helical bore.
A stator body can also be formed by creating a profiled helical bore in relatively thin metal tubing. This formed metal tube can then be used as the stator body by itself, with an injected inner elastomeric layer, or the formed metal tube can be inserted inside into a second body with a longitudinal bore to form the stator body. A stator body with a profiled helical bore can also be formed through other process such as sintering or hot isostatic pressing of powdered materials, for example, a metal, or the profiled helical bore can be machined directly into a body.
It is also desirable to include transducers, including sensors and actuators, in the stator body. The current methods of producing the stator body require complicated machining, etc. of the stator body material, which is typically steel, and therefore are not conducive to providing additional machining for inclusion of the transducers on the finished product. As will be more fully discussed herein, the inclusion of transducers can also aid in the fabrication of stators in a number of ways.
Referring to the particular embodiment of a progressive cavity downhole motor used in drilling operations (e.g., mud motor), the space available for sensing and measuring devices of downhole conditions is limited. The operational portion of a typical bottom hole assembly, including the motors can be relatively long, up to about 9 meters (30 feet) or more. By utilizing the stator of the progressive cavity motor, which heretofore has not contained any sensing or measuring devices, as a carrier of electronics such as transducers then valuable additional space may be claimed for more sophisticated drilling bottom hole assemblies.
Motors are preferably installed as proximal to the drill bit as possible; yet space adjacent the bit is particularly valuable because of its proximity to the newly drilled formation. Transducers, such as a sensor, measuring relevant down hole data as close to the newly drilled formation as possible allows better and more timely well placement decisions to be made, i.e., to control the direction of drilling.
Further, motors undergo significant stress and strain, particularly the load paths through the resilient material layer (e.g., the seal) as it effectively reacts to the bit torque and any forces from downhole transmissions and bearings. For example, some motors can deliver hundreds of kilowatts of power for 200 hours or more at elevated temperatures of about 150° C. (300° F.) or more.
Monitoring the status of the stator and/or the formation and new borehole, such as the temperature, strain and pressure, can allow an assessment of current performance capabilities, e.g., how much power can be generated before the motor might fail, how long is the motor expected to last, and other questions of similar importance to expensive drilling programs.
The disposition of conduits, conductors, and/or pathways which can be used for communicating in electrical, hydraulic and/or mechanical form was previously disclosed in the prior art and are well known to those in this art. See for example U.S. Patent and Trademark Ser. No. 11/496,562, which is incorporated by reference herein.